Extreme pressure lubricating compositions



Patented Mar. .16, 1937 Tammi EXTREME ranssnan LnnmcA'rnyG comosrrronsRobert L. Humphreys and Bruce B. Farrington, Berkeley, Calif., assignorsto Standard Oil Company of California, San Francisco, Calif., acorporation of Delaware No Drawing. Application December 8, 1934, SerialNo. 756,704

15 Claims.

This invention relates to new and useful compositions of matter and tomethods of preparing the same. In particular, it relates to thepreparation of lubricating compositions, particularly of the'type knowngenerally as extreme pressure lubricantsf, such, for example, as willsatisfy the severe requirements demanded in the proper lubrication ofhypoid and the like gears, and hearing surfaces, metal cutting tools,and the like, subjected to unusually heavy loads per unit area ofbearing surface, and has reference to the incorporation in lubricatingcompositions of certain derivatives of organic thio acids.

In generaLtheprimary requirement of such an extreme pressure lubricantis that it shall possess high lubricating film strength; preferably italso has low rates of wear and low coeflicients of friction, and it isan object of the present invention to disclose and provide a novel typeof lubricating composition which fulfills these requirements. It is afurther object of this invention to disclose and provide extremepressure lubricants that do not suffer a loss or deterioration of highfilm strength, low rate of wear, or low coefficients of friction in longcontinued use under severe conditions, and which have no tendency tocause gumming or fouling of the lubricated metal parts or surfaces undersuch long continued service.

As now known, oneclass of compositions designed for use as "extremepressure lubricants comprises mineral lubricating oils to which havebeen added, preferably in oil-soluble form, sufflcient amounts ofvarious active agents discovered to possess the properties of increasingthe film strength and/or of decreasingtwear and/or of decreasingcoeflicients of friction of the mineral base to which they have beenadded. Mineral oil lubricants containing added metallic soaps, notablylead soaps, and/or sulfurized fatty acid or fatty oils, such assulfurized animal or vegetable oils, are examples of such compositions.-Certain of the compositions of this type have thevery serious defectsthat they tend to cause gumming of the metal parts; certain of them tendtoseparate into their constituent parts upon long continued subjectionto severe operating conditions.

Another class of compositions designed for such service, comprisesmineral lubricating oils, either alone or' in admixture with fatty oils,to which have been added sulfur in elemental or uncombined form.Compositions containing such uncombined sulfur have the serious defectsthat they cause undue corrosion and wear of the metal parts to belubricated, or the parts adjacent thereto, such as bushings, etc., whichresult not only in deterioration of the said metal parts, but leaddirectly to a short life of the lubricating compositions themselves.

'We have now discovered that the addition of small amounts of organicderivatives of organic thio acids, particularly the esters andanhydrides of organic thio acids, in admixture with hydrocarbon or fattylubricating oils, provide lubricating compositions which satisfy all ofthe primary requirements of extreme pressure lubricants, and, inaddition, are stable in long continued use, do not separate into theirconstituent parts and do not tend to form gum, or to foul or corrodemetal surfaces.

lhe amounts of the said derivatives of organic thio acids required to beadded to hydrocarbon or fatty lubricating oils for the preparation ofthe compositions of our invention vary somewhat, depending upon theseverity of the service for which they are designed, and, to someextent, upon the character of the hydrocarbon or fatty lubricating stockused as a base; these amounts are in all cases small, however, comparedwith the amounts of active agents of the prior types, and in generalvary between about /2 of 1% and about 5% of the oil base, by weight.

The esters and anliydrides of organic thio acids to be added to mineralor fatty lubricating oils in preparing the compositions of thisinvention correspond to the like derivatives of ordinary carboxylicacids, in which one or more oxygen atoms are replaced by sulfur atoms.They may thus correspond to any one of the following type formulae:

organic radical, whether allsvl, aryl or aralkyl, as well as thefollowing:

'in which anhydrides of thio acids R and R likewise represent anyorganic radical, whether alkyl, aryl or aralkyl.

It will thus be apparent from a consideration of the above type formulaethat the aryl, alkyl and aralkyl esters of the aliphatic thio fattyacids,

such as thio acetic acids, thio valeric acid, thio oleic acid, and thethio naphthenic acids, and the thio carboxylic acids, as well as theanhydrides of these said type thio acids, are contemplated to be addedto mineral'or fatty lubricating oils in preparing therefrom extremepressure lubricating compositions in accordance with our invention.

These compounds are generally oil soluble to the extent required in thepractice of our invention,

and they are likewise generally stable to heat at temperatures of 300 F.or above.

As typical of the results accomplished by the addition of the saidderivatives of organic thio acids to lubricating oils, reference is madeto the accompanying tabulation, in which three distinct types of sulfurlinkage are represented, exempli-r fying each of the types of sulfurlinkage referred to hereinabove and found to be operative to markedlyincrease the film strength of the lubricating compositions in which theyare caused to be present.

In the respective columns in the above tabulation there are set out:First, typical derivatives of thio acids, representative of a greatnumber which may suitably be used in the practice of our invention;second, the type formula of the said thio acid derivatives, particularlysetting out the sulfur linkage therein; third, the amount of combinedsulfur in each of the said thio acid derivatives, in percentage byweight; fourth, the amount of each of the thio acid derivatives added toa mineral hydrocarbon lubricating oil base batch (kept uniform in amounthere only for the purposes of exemplification); fifth, the amount ofsulfur in each of the finished extreme pressure lubricants, inpercentage by weight; sixth, the

film strength of the finished lubricating compositions, as measured onthe Timken machine described by O. L. Maag in the National PetroleumNews for November 16, 1932, page 53, article entitled Extreme pressurelubricants, wherein the O. K. load i Pounds, or the load carryingcapacity of the lubricant, is directly measured. In the aboveexemplifying tabulation the same mineral oil stock was used throughout.

In the preparation of the compositions of our invention, the desiredthio acid derivative or mixture of thio acid derivatives, in suitableamounts, is admixed with a hydrocarbon or fatty mineral oil and theadmixture merely agitated mechanicallyin ordertoobtain completeandhomogeneous solution. We have found in general that the organic estersand the "anhydrides of the organic thio acids are easily soluble inhydrocarbon and fatty oils to the extent required, and that nodifliculty is encountered in incorporating them therein.

A particular feature of our invention lies in the preparation of basesor concentrates containing relatively large amounts of thio acidderivatives in admixture with hydrocarbon or fatty oils. Suchconcentrates may be stored or transported in this form and before actualuse in extreme pressure lubrication service may be diluted with the sameor other lubricating oil to any desired agents in suspended form,however, is sufficientto allow these esters and anhydrides" of theorganic thio acids to function in decreasing film strength in actualuse. 4

Obviously the character and viscosity of the lubricating oil in whichthe thio acid derivatives are added will be dependent to some extentupon the character of service to which the composition is ultimately tobe put, and we are not to be limited in the character of the lubricatingcomposition used as a base in the preparation of our compositions. Forexample, we have found that the life of metal cutting tools is veryremarkably lengthened by the incorporation of small amounts of esters oforganic thio acids and of anhydrides of organic thio acids in either themineral hydro-, carbon or fatty oils used ordinarily in this service.

Moreover, we have prepared miscible metal cut- .ting oils in which theusual oil component is replaced with an oil containing small amounts ofthese thio acid derivatives in solution and have found that the life ofthe cutting tools is greatly lengthened and the character of the metalsurfaces cut much improved, especially in severe cutting service.Further, semi-solid and solid lubricating greases may be prepared, inthe usual manner, wherein small amounts of these thio acid derivativesmay be incorporated in the hydrocarbon and fatty oils-ordinarily usedtherein; the lubricating film strength is in all cases increased to adegree comparable to the increases pointed out in the example tabulatedabove.

While we have described in detail the character of our invention andgiven numerous illustrative examples of the preparation and applicationof the compositions of our invention, we have done so by way ofillustration and with the intention that no limitation should be imposedupon the invention thereby. It will be obvious to those skilledin theart that numerous modifications and variations of the above illustrativeexamples may be effected in the practice of our invention, which is ofthe scope of the claims appended hereto.

We claim:

1. A composition of matter comprising an admixture of a lubricating oiland an organic derivative of an organic thio acid.

2. A composition of matter comprising an admixture of a lubricating oiland a compound of the class consisting of the types in which at leastone oxygen atom is replaced by a sulfur atom, and in which R and Rrepresent any alkyl, aryl or aralkyl radical.

3. Acomposition of matter comprising an admixture of a hydrocarbonlubricating oil and an organicderivative of an organic thio acid.

4. A composition of matter comprising an admixture of a hydra arbonlubricating oil and an organic ester of an organic thio acid.

5. A composition of matter comprising an admixture of a hydrocarbonlubricating oil and an "anhydridef of an organic thio acid.

6. A composition of matter comprising a lubricatlng oil containingbetween about 0.5 and about 5.0 per cent by weight of an organicderivative of an organic thio acid.

7. A lubricating composition containing a lubricating oil and an ethylthio benzoate.

8. A lubricating composition containing a. lubricatingoil and benzylthiobenzoate.

9. An extreme pressure lubricant base comprising an oil and an organicderivative of a thio acid, capable of dilution with a lubricating oil toproduce an extreme pressure lubricant containing between about 0.5 andabout 5.0 per cent by weight of the said thio acid derivative.

10. An extreme pressure lubricant base containing 50 or more per cent byweight of an organic derivative of a thio acid in admixture with an oil.

11. A composition of matter consisting of a hydrocarbon lubricating oiland a compound of the class consisting of the types-- in which at leastone oxygen atom is replaced by 12. A composition of matter consisting ofa hydrocarbon lubricating oil containing between about 0.5 and about 5.0per cent by weight of a compound of the class consisting of the types 6I? u R-OO-R and RCOC-R in which one or more oxygen atoms are replaced bysulfur atoms, and in which R. and R represent any alkyl, aryl or aralkylradicals.

13. A lubricating composition comprising a lubricating oil containingbetween about 0.5 and about 5.0 per cent by weight of an ethyl thiobenzoate.

14. A lubricating composition comprising a lubricating oil containingbetween about 0.5 and about 5.0 per cent by weight of a benzyl thiobenzoate.

15. An extreme pressure lubricant base comprising an oil containing an.organic ester of an organic thioacid, capable of dilution with alubricating oil to produce an extreme pressure lubricant containingbetween about 0.5 and about- '5.0'per cent by weight-of the said organicester of the said organic thioacid.

ROBERT 1.. HUMPHREYS. BRUCE B. FARRINGTON.

